The evolution of menstruation in primates

ongoing

Menstruation is a recent evolutionary innovation in primates: the trait is present in some species (humans, baboons) but not in closely related others (orangutans, vervets). In the latter and in most mammals, the uterine endometrium is reabsorbed at the end of the cycle instead of being shed when fecundation has not occurred. The molecular and genetic underpinnings of this complex process are not fully understood, despite its critical involvement in gynaecological conditions. I propose to discover the molecular mechanisms leading to menstruation by comparing the uterine linings from five primate species at the cellular, functional and genetic levels. The objectives are to identify the gene networks and non-coding regulatory elements that control the advent of menstruation in primates, and to understand how this genetically inherited trait was acquired in primate genomes during the evolution of the human lineage. In Aim 1, I will leverage single-cell transcriptomics to uncover the cellular composition and marker modifications that differentiate the uterine linings of menstruating and non-menstruating primates. In Aim 2, I will use deep transcriptomics and accessible chromatin assays on sorted endometrial cell populations to identify genes and non-coding regulatory regions differentially activated in menstruating species. This analysis will reveal the molecular pathways, regulation networks and cellular interplay involved in uterine tissue shedding vs. reabsorption. In Aim 3, I will replace these modifications within the context of primate genome evolution: I will elucidate the mutational dynamics by which genetic novelty has emerged during the adoption of menstruation, and how the functional divergence of the endometrium compares to other reproductive and somatic tissues. This project will enhance our understanding of a key physiological trait for human reproduction as well as a dramatic example of functional innovation in the primate lineage.